Jake Long

Jake Long is a 27-year-old four-time Pro Bowler who has started 74 out 80 possible games in his five-year career.

Guys like that don't hit the open market, and yet the Miami Dolphins elected to let him walk.

Presumably, the Dolphins decided to let Long test the free-agent waters because of his injuries, which have resulted in him ending consecutive seasons on the injured reserve.

But Long's decline in production this past season factors into the equation.

Had Long been a free agent after the 2011 season, he would have commanded one of the largest contracts for an offensive lineman in NFL history. But just a year later, teams are unsure of his true value.

Potential free-agent suitors will need to determine how much of Long's decline in production was a result of lingering injury issues, and how likely those issues are to pop up again.

Andre Smith

Andre Smith, the former sixth overall selection in 2009, has flashed the ability to be a dominant right tackle. But he had never fully lived up to expectations until the 2012 season.

This past year, Smith finally put it all together and emerged as one of the game's elite run-blockers on the right side. According to Pro Football Focus, Smith ranked as the third-best run-blocking right tackle in 2012.

As strong as Smith was this past season, there are good reasons to wonder if he was simply motivated by his impending free agency.

Smith has struggled with weight issues throughout his career, dating back to his days at Alabama.

He's been rumored to weigh anywhere from 370 to 330 pounds at various points in his career.

Whoever signs Smith runs the risk that a new contract will deplete his motivation to stay in shape, causing him to revert back to his inconsistent performances from early in his career.

Brent Grimes

Midway through the 2011 season, Brent Grimes was in the midst of establishing himself as one of the premier cornerbacks in the league.

Since that time, he's undergone surgery on his knee and missed nearly the entire 2012 season due to an Achilles injury.

Now Grimes, who turns 30 in July, is coming off two injuries as he hits the free-agent market, raising questions about his long-term value.

If fully healthy, Grimes could provide a significant spark to a team's secondary. But investing in him at this stage of his career is a gamble.

The fact that the Atlanta Falcons allowed Grimes to hit the open market, despite a glaring weakness at cornerback following the release of Dunta Robinson, may be a telling sign as to their view of Grimes' health.

Harrison was slowed by a knee injury this past season after undergoing surgery in August. He also claims to have suffered at least 10 concussions throughout the course of his career, according to a report by ESPN.

However, the injuries are only part of the concern surrounding Harrison.

He's an outspoken personality who has dealt with multiple off-field issues throughout his career. Additionally, he refused to take a pay cut to stay with the Pittsburgh Steelers, and it's reasonable to wonder how he'll handle a reduced role when that time comes.

The Steelers learned how to handle Harrison over his decade-long career in Pittsburgh, but his new franchise won't necessarily know how to best deal with his difficult personality.

It's only a matter of time before he causes some sort of off-field distraction, and some teams may simply not want to bring that into the locker room.

Rashard Mendenhall

It's not often that a potential feature back hits the open market at the age of just 25 years old, so there are plenty of reasons to be intrigued by Rashard Mendenhall.

However, Mendenhall's season has ended with a trip to the injured reserve in two of his five years in the league. And that doesn't even include the 2012 season, in which he played just six games.

To make matters worse, Mendenhall was also suspended for a game by the Steelers for conduct detrimental to the team when he failed to show up for a game after being ruled inactive.

Mendenhall's attitude in 2012 could scare some teams away.

Due to the injuries, Mendenhall won't be guaranteed a starting job. And the way he handled a reduced role with the Steelers this past season will make teams wonder if he's more trouble than he's worth in a backup role.